EP3277525B1 - Tyre comprising a textured tread - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a tire, the top of which comprises a tread provided with grooves with textured zones.

STATE OF THE PRIOR ART

In order to preserve the level of safety of a vehicle, it is advisable to check the level of tire wear regularly, and preferably before each long journey. For this, the motorist observes the surface of the tread of the tires and measures the height of the treads. This measurement is facilitated by an element present on any type of tire: the wear indicator. The wear indicator allows the wear condition of the tires to be assessed on the basis of a reliable reference. This indicator is typically placed in the grooves of the tires. So when the tread patterns are at the same height as the wear indicators, (for example, in Europe, at least 1.6 millimeters in height compared to the furrow bottom), it is advisable to replace the tire (s).

The wear indicator is installed at the bottom of the grooves and is generally in rectangular form. It must be visible not only to the user, but also to third parties, for example in order to allow the compliance of the wear indicators with the legislation. It is therefore important to have effective and reliable visual cues to allow the wear indicators to be located quickly and easily. In certain cases, the wear indicators of certain passenger vehicle tires, in particular the models with the chassis lowered, are less visible insofar as bodywork elements cover the upper part of the tires. In this situation, the wear indicator becomes less visible. The user can then identify the location of the wear indicator by referring to a marker located in the shoulder area. Such a mark can be constituted by the well-known symbol "TWI" (meaning in English "Tire Wear Indicator", or in French: wear indicator), or any other symbol easily recognizable by users.

In other cases, the grooves in the tread are completely covered with light-absorbing textures, making locating the wear indicator difficult, sometimes even very difficult. The documents JPH0699705 , EP1568514 , JP2004196145 disclose grooves having a plurality of protruding elements.

For example, the patent application US6866076 describes a tire intended to reduce the resistance to flow of a fluid in the grooves. To this end, the tire has textures at the bottom of the grooves. The tire grooves are covered with small grooves or ribs having a fixed depth in the range of 0.01 to 0.5 millimeters. Thus, the resistance to flow of water in the groove is reduced. Thanks to this type of arrangement, it is possible to improve the performance of the tire, for example in a wet environment. However, with such an arrangement, the wear indicator, arranged among the grooves, is barely visible. Furthermore, the presence of the grooves near the wear indicators can make it difficult to check the height of the wear indicators. In fact, the grooves constitute obstacles which can affect the correct positioning of a measuring tool such as a slide bar, a micrometer, or a calliper, which can cause inaccurate measurements.

To overcome these different drawbacks, the invention provides different technical means.

STATEMENT OF THE INVENTION

First of all, a first object of the invention consists in providing a tire arranged to facilitate the identification or the localization of the wear indicators of the tread.

Another object of the invention is to facilitate the verification of the compliance of the wear indicators with legal requirements.

Finally, another object of the invention consists in making it possible to measure the height of the wear indicators positioned in a textured sector.

To do this, the invention provides a tire comprising a tread, the tire comprising at least one groove, at least one wear indicator disposed in the groove, the wear indicator comprising a contact face intended to enter into contact with a roadway when the tire reaches a limit level of wear, the groove comprising a texture made of material with a bottom of this groove, said texture surrounding the wear indicator and making contrast with the contact face of the indicator wear. The wear indicator comprises at least one lateral face connecting the contact face of the wear indicator to said bottom. The groove has an area devoid of texture, disposed between an area provided with texture and a side face of the wear indicator, said area devoid of texture comprising a length of between 3 and 10 mm.

Thus the textured surfaces of the grooves absorb light. Conversely, the smoother surfaces of the wear indicators allow better light reflection. This effectively creates a contrast between the two surfaces and makes the wear indicator (s) more visible. The user can thus identify or locate the wear indicators of his tires with greater ease, making checking the wear of the tires less tedious.

Advantageously, the texture has a brightness called first brightness (L * 1), the contact face of the wear indicator has a brightness called second brightness (L * 2), the difference in brightness between the first and second brightness being at least 5 brightness units (on a scale varying from 0 to 100). Such a difference in brightness makes it possible to create a contrast effect that is easily identifiable for a user. This contrast effect can advantageously be used to locate a specific point such as a wear indicator, conventionally difficult to spot on a tread without a contrast effect.

The first brightness (L * 1) is advantageously between 5 and 18 units, and preferably between 8 and 16 units. The values tend towards black, so as to absorb the incident light well.

The brightness of the contact face (or second brightness) is between 20 and 35 units. The values tend towards white, so as to reflect the incident light well.

Such a zone advantageously serves as a measurement zone, making it easier to check the conformity of the height H of the wear indicator, for example during a step of checking out of the mold. The non-textured appearance of the measurement area allows precise and certain control of the height H of the wear indicator.

Alternatively, the texture is hollow relative to the bottom of the groove. Such a recessed arrangement reduces the risk of disturbing the flow of water flow and does not disturb the measurement of the height H of the wear indicator.

DEFINITIONS

By "pneumatic" is meant all types of elastic tires subjected to internal pressure or not.

By “rubber material” is meant a diene elastomer, that is to say in a known manner an elastomer derived at least in part (that is to say homopolymer or a copolymer) from diene monomers (carrier monomers of two carbon-carbon double bonds, conjugated or not).

By “tread” of a tire is meant an amount of rubber material delimited by lateral surfaces and by two surfaces main ones, one of which, called the rolling surface, is intended to come into contact with a roadway when the tire is rolling.

By “sidewall” of a tire is meant a lateral surface of the tire disposed between the tread of the tire and a bead of this tire.

By “texture” is meant an organized arrangement of a plurality of elements, all or part of the elements of the arrangement being the repetition of the same basic element, for example, a strand or a strip.

By "strand" is meant a filiform element whose height is at least equal to twice the diameter of a disc with the same surface area as the average section of the strand.

By "lamellae" is meant elongated strands which have a length at least equal to twice their height.

By “luminosity” or “luminance”, one understands the parameter which characterizes a surface to reflect more or less light. Brightness is expressed on a scale ranging from 0 to 100 according to the L * a * b * color model established by the CIE (International Commission on Lighting) in 1976. The value 100 represents white or total reflection; the value 0, black or total absorption. In this color model a * and b * are chromaticity coordinates. The L * a * b * color model also defines a chromaticity diagram. In this diagram, a * and b * indicate the direction of the colors: + a * goes towards red, -a * towards green, + b * towards yellow, and -b * towards blue. The center of the diagram is achromatic. As the values a * and b * increase, and as we move away from the center of the diagram, the saturation increases.

DESCRIPTION OF THE FIGURES

• la figure 1 est une vue partielle d'une bande de roulement d'un pneumatique selon l'invention ;
• la figure 2 est une vue en coupe d'un exemple de témoin d'usure selon l'art antérieur ;
• la figure 3 est une vue en coupe d'une variante de réalisation du témoin d'usure de la figure 2 selon l'art antérieur ;
• les figures 4 et 5 sont des vues en coupe de deux exemples de témoins d'usure non texturés entourés de zones de mesure également non texturées, insérés au sein d'une rainure texturée ;
• la figure 6 représente une partie de la texture de la rainure selon un premier exemple de réalisation selon lequel la texture présente des éléments en protubérance en forme de brins ;
• la figure 7 représente une partie de la texture de la rainure selon un second exemple de réalisation dans lequel la texture présente des éléments en protubérance en forme de lamelles ;
• la figure 8 représente une partie de la texture de la rainure, selon un troisième exemple de réalisation dans lequel la texture présente des éléments en protubérance en forme de parallélépipèdes ;
• la figure 9 représente une partie de la texture de la rainure, selon un quatrième exemple de réalisation dans lequel la texture présente des éléments en protubérance dont les formes et les distances entre éléments en protubérance sont variables ;
• la figure 10 représente une partie de la texture de la rainure, selon un cinquième exemple de réalisation dans lequel la texture présente des éléments en creux, coniques dans cet exemple ;
• la figure 11 représente une vue agrandie d'une cavité d'un élément en creux de la texture de la figure 10.

All the details of realization are given in the description which follows, supplemented by the Figures 1 to 11 , presented only for the purposes of nonlimiting examples, and in which:

• the figure 1 is a partial view of a tread of a tire according to the invention;
• the figure 2 is a sectional view of an example of a wear indicator according to the prior art;
• the figure 3 is a sectional view of an alternative embodiment of the wear indicator of the figure 2 according to the prior art;
• the Figures 4 and 5 are sectional views of two examples of non-textured wear indicators surrounded by also non-textured measurement zones, inserted within a textured groove;
• the figure 6 represents a part of the texture of the groove according to a first exemplary embodiment according to which the texture has elements in protrusion in the form of strands;
• the figure 7 represents a part of the texture of the groove according to a second embodiment in which the texture has protruding elements in the form of lamellae;
• the figure 8 represents a part of the texture of the groove, according to a third embodiment in which the texture has elements protruding in the form of parallelepipeds;
• the figure 9 represents part of the texture of the groove, according to a fourth embodiment in which the texture has protruding elements whose shapes and distances between protruding elements are variable;
• the figure 10 represents a part of the texture of the groove, according to a fifth embodiment in which the texture has hollow elements, conical in this example;
• the figure 11 represents an enlarged view of a cavity of a hollow element of the texture of the figure 10 .

DETAILED DESCRIPTION OF THE INVENTION

The figure 1 is a schematic representation of a portion of a tread 8 of a tire 1. The tread 8 provides a surface for contact with the ground made up of vertices 9 of treads. The bottoms 10 of tire treads 1 form grooves 2, or grooves. The grooves 2 serve as housing in order to position the wear indicators 3. The grooves 2 can also be arranged in different ways in order to respond to specific functions. In the example illustrated, the grooves 2 are circumferential and provided with textures 4 at the bottom 10 of grooves. Such a coating has many functional and visual advantages. However, it is likely to affect the visibility of the wear indicators 3. Thus, according to the invention, and as illustrated, the wear indicators 3, in particular the contact faces 7 of the wear indicators, are advantageously devoid of textures, and have a surface producing a brightness contrast with the adjacent surface of the textured grooves. The contrast effect between the bottom of the grooves and the wear indicators 3 makes the latter clearly visible, thus facilitating their location. Such a characteristic is particularly advantageous when the tread 8 is in a context where visibility is restricted.

As illustrated in figure 2 , the non-textured wear indicator 3 is arranged in a groove 2 provided with a texture 4, in accordance with the prior art. The absence of texture on the wear indicator 3 creates an accentuated contrast compared to the textured groove 2.

A wear indicator 3 may include textured surfaces, such as for example a side face 6. The figure 3 illustrates such an embodiment in accordance with the prior art. It is however preferable that the contact face 7 (or functional part) of the wear indicator is non-textured so that the contrast with the texture of the groove 4 is accentuated. The integration of non-textured wear indicators 3 within textured grooves 4 has the effect of accentuating the visibility of the wear indicators 3 by the effects of contrasts, in particular of brightness. The wear indicators 3 are thus better visible.

The contrast effect previously mentioned comes from the fact that the brightness of the areas provided with textures is lower than that of the areas devoid of textures. Various arrangements or configurations of textures 4 make it possible to produce such an effect, as described below, in relation to the Figures 6 to 11 .

• la luminosité L*1, L*2 des zones de la rainure (zones recouvertes par la texture, zones non recouvertes par la texture) ;
• une composante a* qui définit une première nuance de couleur entre le rouge et le vert ;
• une composante b* qui définit une deuxième nuance de couleur entre le jaune et le bleu.

On positionne ledit appareil sur la partie du pneumatique que l'on veut mesurer et ledit appareil donne les valeurs des trois paramètres L*, a*, b* relatifs à la texture. Ces mesures sont effectuées avec le mode « SCI » (Mode de réflexion spéculaire incluse) paramétré à un angle de 10° et un réglage de la lumière de type D65 (réglage défini selon la Commission Internationale de l'Eclairage, CIE). Grâce à cet appareil, on quantifie la luminosité des textures de la rainure 4 qui est ensuite comparée à la luminosité des parties non texturées du témoin d'usure.The appropriate luminosity measuring device is a CM 700D spectro-colorimeter from the brand KONICA-MINOLTA, (registered trademark). This device is suitable for measuring:

• the luminosity L * 1, L * 2 of the areas of the groove (areas covered by the texture, areas not covered by the texture);
• a component a * which defines a first shade of color between red and green;
• a component b * which defines a second shade of color between yellow and blue.

Said device is positioned on the part of the tire that is to be measured and said device gives the values of the three parameters L *, a *, b * relating to the texture. These measurements are carried out with the “SCI” mode (Specular reflection mode included) configured at an angle of 10 ° and a D65 type light adjustment (adjustment defined according to the International Commission on Lighting, CIE). With this device, the brightness of the textures of the groove 4 is quantified, which is then compared to the brightness of the non-textured parts of the wear indicator.

The arrangement favoring the visibility of the wear indicators 3 at the bottom of the groove 4 previously described can be advantageously used for any type of tire 1.

The Figures 4 and 5 illustrate schematic sectional representations of an embodiment of the wear indicators 3 according to the invention. Non-textured zones 5 are released in the immediate vicinity of the wear indicator 3 in order to allow very precise measurement of the height H thereof in a certain and repetitive manner during a step of checking the wear indicator during the process tire manufacturing. In the example of realization of the figure 4 , the base of the textures in the bottom of the groove 10 is located in the same radial position as the measurement zone 5 adjoining the wear indicator 3. In the example of the figure 5 , the tops of the textures of the groove are located at the same radial position as the measurement zone 5 adjoining the wear indicator 3. In these two embodiments, the measurement zone is substantially flat and devoid of textures.

The Figures 6 to 11 illustrate examples of textures 4 which can be arranged on the groove 2 according to the invention.

The figure 6 illustrates an embodiment in which the texture comprises a plurality of strands 11. The strands 11 are distributed in the texture at a density at least equal to one strand per mm ² , each strand having an average section S of between 0.0005 mm ² and 1 mm ² . It is noted that the mean section of each strand corresponds to the mean of the sections S measured at regular intervals from the base of the strand. The strands have a generally conical shape with a section decreasing in the height Hb of these strands.

The figure 7 illustrates an embodiment in which the texture comprises a plurality of blades 12 parallel to each other, the pitch of the blades 12 in the texture being at most equal to 0.5 mm, each blade 12 having an average width of between 0.02 mm and 0.5 mm. It is noted that the average width corresponds to the average of the widths l measured at regular intervals in the height H1 of the blade, the height of each blade being between 0.05 and 0.5 mm.

In another alternative embodiment, the texture comprises a combination of strands 11 and / or and of blades 12.

The invention is not limited to the examples described and shown and various modifications can be made thereto without departing from its scope. Thus, according to another non-limiting alternative embodiment, the blades 12 of the figure 7 may be discontinuous. They have a flat part between them. They may also have cross-section differences between them. In addition, the blades can have curvatures or angles, especially in their length. They can also be of variable length.

In the example of the figure 8 , the textures have a parallelepipedic section 13 of side C of between 0.05 mm and 0.5 mm, of height Hp of between 0.05 mm and 0.5 mm, the distance Dp between two adjacent cavities in the texture being included between 0.05 mm and 0.5 mm. As a variant, the texture section can be circular, polygonal (for example hexagonal). With square or polygonal structures, it is possible to organize the elements more easily with respect to each other so as to limit the surface of the intermediate zones between the elements.

In the variant of the figure 9 , the elements 14 have variable shapes and distances between them. This variant makes the details of texture 4 less visible.

The figure 10 illustrates a texture according to another non-limiting alternative embodiment. In this variant, the texture is formed by a plurality of cavities 16. The cavities 16 are here in the form of cones which extend into the depth of the surface and open onto this surface by forming circular openings 15. The cavities 16 thus have a section which decreases in depth. Note that in this variant, the openings 15 of the cavities 16 do not touch. The openings 15 are separated by intermediate zones 17. In addition, the openings 15 are regularly distributed so that the distance d between each opening 15 is generally similar.

The figure 11 is an enlarged view of the texture of the figure 10 . All or part of the cavities here has at least one wall 18 which, according to a sectional view, forms an angle β between 10 ° and 60 ° relative to a direction Z perpendicular to the texture.

The Figures and their descriptions made above illustrate the invention rather than limit it.

The reference signs in the claims have no limiting character. The verbs "understand" and "comprise" do not exclude the presence of elements other than those listed in the claims.

Reference numbers used in the figures

1

Pneumatic

2

Groove

3

Wear indicator

4

Texture

5

Texture-free area

6

Face of the wear indicator

7

Wear indicator contact face

8

Tread

9

Tread sculpture top

10

Groove bottom

11

Strands

12

Blades

13

Parallelepiped section

14

Protruding elements

15

Openings

16

Cavities

17

Intermediate areas

18

Cavity wall

Claims (9)

1. Tyre (1) comprising a tread (8), the tyre comprising at least one groove (2), at least one wear indicator (3) disposed in the groove (2), the wear indicator comprising a contact face (7) intended to come into contact with a roadway when the tyre reaches a wear limit, the groove (2) comprising a texture (4) produced integrally with a bottom (10) of this groove (2), said texture (4) being an organized arrangement of a plurality of elements, all or some of the elements of the arrangement being the repetition of a single base element, such as a strand or a lamella, said texture (4) surrounding the wear indicator (3) and contrasting with the contact face (7) of the wear indicator, the wear indicator (3) comprising at least one lateral face (6) connecting the contact face (7) of the wear indicator to said bottom (10), characterized in that the groove (24) has a texture-free zone (5) disposed between a zone provided with a texture (4) and the lateral face (6) of the wear indicator, said texture-free zone (5) having a length of between 3 and 10 mm.
2. Tyre according to Claim 1, wherein the texture (4) has a lightness known as first lightness (L*1) and the contact face (7) of the wear indicator has a lightness known as second lightness (L*2), characterized in that the difference in lightness between the first and second lightness is at least 5 units of lightness, lightness being the parameter which characterizes a surface to reflect light to a greater or lesser extent, said lightness being expressed using a scale that ranges from 0 to 100 according to the L*a*b* colour model established by the International Commission on Illumination in 1976.
3. Tyre (1) according to Claim 2, wherein the first lightness (L*1) is between 5 and 18 units, preferably between 8 and 16 units.
4. Tyre (1) according to one of Claims 2 or 3, wherein the lightness of the contact face (7) is between 20 and 35 units.
5. Tyre (1) according to one of Claims 1 to 4, said lateral face (6) not having said texture (4).
6. Tyre (1) according to any one of Claims 1 to 5, wherein the texture (4) comprises a plurality of strands (11), said strands (11) being distributed through the texture at a density at least equal to one strand per mm², each strand having a mean cross section S of between 0.0005 mm² and 1 mm².
7. Tyre (1) according to any one of Claims 1 to 6, wherein the texture (4) comprises a plurality of mutually parallel blades (12), the spacing of the blades (12) in the texture (4) being at most equal to 0.5 mm, each blade 12 having a mean width of between 0.02 mm and 0.5 mm.
8. Tyre (1) according to any one of Claims 1 to 7, wherein the textures have a parallelepipedal cross section (13) with a side length C of between 0.05 mm and 0.5 mm and a height Hp of between 0.05 mm and 0.5 mm.
9. Tyre (1) according to any one of Claims 1 to 8, wherein the texture (4) is formed by a plurality of cavities (16), said cavities (16) being in the form of cones, said cavities extending into the depth of the surface and opening onto said surface, forming circular openings (15).

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